code: def __str__(self) -> str:
      expr_str = "("
      if self.get_child(0):
          expr_str += f"{self.get_child(0)}"
      if self.etype:
          expr_str += f" {self.get_symbol()} "
      if self.get_child(1):
          expr_str += f"{self.get_child(1)}"
      expr_str += ")"
      return expr_str
  
file_path: evadb/evadb/expression/comparison_expression.py
imports: from evadb.expression.abstract_expression import AbstractExpression, ExpressionReturnType, ExpressionType
  from evadb.models.storage.batch import Batch
label_desc: Use image node_id 4 for calling the ComparisonExpression obj's underlying member method code with example usage: obj.__str__() and returns: expr_str